Ridley was chairman of the UK bank Northern Rock from 2004 to 2007, during which period Northern Rock experienced the first run on a British bank in 150 years. Ridley chose to resign, and the bank was bailed out by the UK government leading to the nationalisation of Northern Rock.[11]

Ridley joined The Economist in 1984, first working as a science editor until 1987, then as Washington, D.C. correspondent from 1987 to 1989 and as American editor from 1990 to 1992.[13][14] He was a columnist for Daily Telegraph and Sunday Telegraph and an editor of The Best American Science Writing 2002.[15]

From 2010 to 2013, Ridley wrote the weekly "Mind and Matter" column for the Wall Street Journal, which "explores the science of human nature and its implications".[18]

Since 2013 Ridley has written a weekly column for The Times on science, the environment, and economics.[10][19]

Ridley wrote the majority of the main article of the August 2017 BBC Focus edition[20]. The article explains his scepticism regarding Resource depletion, challenging the widespread belief that resource depletion is an important issue. He cites various previous resource scares as his evidence.

He had been[when?] a governor of the Ditchley Foundation, which organises conferences to further education and understanding of Britons and North Americans.[23] He participated in a February 2000 Ditchley conference.[24]

The Banks Group and Blagdon estate developed and sponsored the construction of Northumberlandia, or the Lady of the North, a huge land sculpture in the shape of a reclining female figure, which was part-commissioned and sponsored by Ridley.[26] Now run by a charity group called the Land Trust,[27] it is the largest landform in the world depicting the human form, and, through private funding, cost £3m to build.[28][29] Attracting over 100,000 people per year, the Northumberland art project, tourism and cultural landmark has won a global landscape architecture award and has been named ‘Miss World’.[30]

The Rational Optimist primarily focuses on the benefits of the innate human tendency to trade goods and services. Ridley argues that this trait is the source of human prosperity, and that as people increasingly specialize in their skill sets, we will have increased trade and even more prosperity.[33] This was shortlisted for the 2011 BBC Samuel Johnson Prize.[34]

2010 TED conference talk, "When Ideas Have Sex", received over 2 million views.[35] Ridley argues that exchange and specialisation are the features of human society that lead to the development of new ideas, and that human society is therefore a "collective brain".[36]

In The Evolution of Everything, Ridley "makes the case for evolution, rather than design, as the force that has shaped much of culture, technology and society, and that even now is shaping our future.” He argues that "Change in technology, language, mortality and society is incremental, inexorable, gradual and spontaneous…Much of the human world is the result of human action, but not of human design; it emerges from the interactions of millions, not from the plans of a few."[42]

In a 2006 edition of the on-line magazine Edge - the third culture, Ridley wrote a response to the question "What's your dangerous idea?" which was entitled "Government is the problem not the solution",[43] in which he describes his attitude to government regulation: "In every age and at every time there have been people who say we need more regulation, more government. Sometimes, they say we need it to protect exchange from corruption, to set the standards and police the rules, in which case they have a point, though often they exaggerate it... The dangerous idea we all need to learn is that the more we limit the growth of government, the better off we will all be."

In 2007, the environmentalist George Monbiot wrote an article in The Guardian connecting Ridley's libertarian economic philosophy and the £27 billion failure of Northern Rock.[44] On 1 June 2010 Monbiot followed up his previous article in the context of Matt Ridley's book The Rational Optimist, which had just been published. Monbiot took the view that Ridley had failed to learn from the collapse of Northern Rock.[45]

Ridley has responded to Monbiot on his website, stating "George Monbiot’s recent attack on me in the Guardian is misleading. I do not hate the state. In fact, my views are much more balanced than Monbiot's selective quotations imply."[46] On 19 June 2010, Monbiot countered with another article on the Guardian website, further questioning Ridley's claims and his response.[47] Ridley was then defended by Terence Kealey in a further article published on the Guardian website.[48]

In November 2010, the Wall Street Journal published a lengthy exchange between Ridley and the Microsoft founder Bill Gates on topics discussed in Ridley's book The Rational Optimist.[49][50] Gates said that "What Mr. Ridley fails to see is that worrying about the worst case—being pessimistic, to a degree—can actually help to drive a solution"; Ridley said "I am certainly not saying, 'Don't worry, be happy.' Rather, I'm saying, 'Don't despair, be ambitious.'"

Ridley summarised his own views on his political philosophy during the 2011 Hayek Lecture: "[T]hat the individual is not – and had not been for 120,000 years – able to support his lifestyle; that the key feature of trade is that it enables us to work for each other not just for ourselves; that there is nothing so anti-social (or impoverishing) as the pursuit of self sufficiency; and that authoritarian, top-down rule is not the source of order or progress."[51]

In an email exchange, Ridley responded to the environmental activist Mark Lynas' repeated charges of a right-wing agenda with the following reply:

On the topic of labels, you repeatedly call me a member of "the right". Again, on what grounds? I am not a reactionary in the sense of not wanting social change: I make this abundantly clear throughout my book. I am not a hierarchy lover in the sense of trusting the central authority of the state: quite the opposite. I am not a conservative who defends large monopolies, public or private: I celebrate the way competition causes creative destruction that benefits the consumer against the interest of entrenched producers. I do not preach what the rich want to hear — the rich want to hear the gospel of Monbiot, that technological change is bad, that the hoi polloi should stop clogging up airports, that expensive home-grown organic food is the way to go, that big business and big civil service should be in charge. So in what sense am I on the right? I am a social and economic liberal: I believe that economic liberty leads to greater opportunities for the poor to become less poor, which is why I am in favour of it. Market liberalism and social liberalism go hand in hand in my view.[52]

Ridley has long argued for a "lukewarm" view of climate change and against renewable energy policies that he considers damaging to the economy as well as the environment. In a report for the Global Warming Policy Foundation in 2013 he wrote:

I have written about climate change and energy policy for more than 25 years. I have come to the conclusion that current energy and climate policy is probably more dangerous, both economically and ecologically, than climate change itself. This is not the same as arguing that climate has not changed or that mankind is not partly responsible. That the climate has changed because of man-made carbon dioxide I fully accept. What I do not accept is that the change is or will be damaging, or that current policy would prevent it.[54]

Ridley has consistently argued that the evidence suggests that carbon dioxide emissions are currently doing more good than harm, largely because of the CO2 fertilisation effect, which boosts crop growth and the growth of forests and wild vegetation, and that the best evidence suggests this will continue to be the case for many decades. In 2015 he wrote about a report by the independent scientist Indur Goklany as follows:

As Goklany demonstrates, the assessments used by policy makers have overestimated warming so far, underestimated the direct benefits of carbon dioxide, overestimated the harms from climate change, and underestimated the human capacity to adapt.[55]

In 2014, a Wall Street Journal op-ed written by Ridley was sharply challenged by Jeffrey Sachs of Columbia University's Earth Institute. Sachs termed "absurd" Ridley's characterization of a paper in Science magazine by two scientists Xianyao Chen and Ka-Kit Tung. Sachs cited the data from the Science article to rebut Ridley's contentions, and stated that the "paper's conclusions are the very opposite of Ridley's".[56][57] Ridley replied that 'it is ludicrous, nasty and false to accuse me of lying or "totally misrepresenting the science..I have asked Mr. Sachs to withdraw the charges more than once now on Twitter. He has refused to do so ...."'[58]

He gave the 2016 Global Warming Policy Foundation annual lecture on “Global warming versus global greening”, in which he said:

I published an article in the Wall Street Journal in January 2013 on these various lines of evidence, including Myneni’s satellite analysis, pointing to the increase in green vegetation. This was probably the very first article in the mainstream media on the satellite evidence for global greening.[59]

Ridleys views on climate change have been criticised by Friends of the Earth because he has connections to the coal industry. He is the owner of land in the north east of England on which the Shotton Surfacecoal mine operates, and receives payments for the mine. In 2016 he was accused of lobbying for the coal industry.[60] This was summarily dismissed by the Parliamentary Commissioner for Standards.[61]

Ridley was one of the earliest commentators to spot the economic significance of shale gas. In his 2011 report, "The Shale Gas Shock", for the Global Warming Policy Foundation, he wrote that:

shale gas will undoubtedly prove to be a significant new force in the world energy scene, with far-reaching consequences.[62]

Ridley is a forthright proponent of fracking.[63] However he has been found to have breached the Parliamentary Code of Conduct by the House of Lords Commissioner for Standards for not orally disclosing in debates on the subject personal interests worth at least £50,000 in Weir Group,[64] which has been described as, 'the world's largest provider of special equipment used in the process' of fracking.[65]

In 2011, the Manhattan Institute awarded Ridley their $50,000 Hayek Prize for his book, The Rational Optimist. In his acceptance speech, Ridley said: "As Hayek understood, it is human collaboration that is necessary for society to work... the key feature of trade is that it enables us to work for each other not just for ourselves; that attempts at self-sufficiency are the true form of selfishness as well as the quick road to poverty; and that authoritarian, top-down rule is not the source of order or progress."[73] In 2011, Ridley gave the Angus Millar Lecture on "scientific heresy" at the Royal Society of Arts (RSA) .[74]

In 2012, Ridley became the 5th Viscount Ridley and Baron Wensleydale on the death of his father.[1] He is also the 9th Baronet Ridley.[75] In 2013, he was elected as hereditary peer in the House of Lords as a member of the Conservative Party.[76]

Dr Mathew Ridley has made major contributions to public engagement with the biological sciences. He was one the founders and the first chairman of the Centre for Life in Newcastle which combines research, commercial application, schools education, ethical debate and a pioneering interactive life-science exhibition, The Centre has attracted over half a million visitors since it opened in 2000 and has given more than 30,000 school children a taste of biology in “Lifelab”, its school-age teaching lab. It has recently achieved a landmark with the creation of the first embryonic stem cell line. Ridely is well known for his popular books and extensive writings about biological sciences. His book “Genome: the autobiography of a species in 23 chapters” had sold over half a million copies and his “Nature via Nurture: genes, experience and what make us human” recasts the nature-nuture debate and argues that nurture works through genes as much as nature does. He is a profound influence on biomedical science and society.[3]